全部计数<；br/>；并用php替换数字4

我有像这样的文字

"Hello, Hello, how are you?
Hello, Hello, how are you?<br />
Hello,
Hello,<br />
How are you?
How are you today?
I am fine; I am great
I am fine;<br />
I am just great
I am fine; I am great
I'm very well today!<br />
Great!
Hello, Hello, how are you?<br />
Hello, Hello, how are you?
Hello, Hello, How are you?<br />
How are you today?"

但这是唯一一个找到的

我尝试替换数字4

尝试以下操作：

<?php

$txt  = "Hello, Hello, how are you?
Hello, Hello, how are you?<br />
Hello,
Hello,<br />
How are you?
How are you today?
I am fine; I am great
I am fine;<br />
I am just great
I am fine; I am great
I'm very well today!<br />
Great!
Hello, Hello, how are you?<br />
Hello, Hello, how are you?
Hello, Hello, How are you?<br />
How are you today?";

$occurrences = substr_count($txt, '<br />');
if( 1 === $occurrences ) {
    $txt = str_replace('<br />', "<img>", $txt);
} else {
    $counter = 1;
    $txt = preg_replace_callback("/<br \/>/", function ($m) use (&$counter) {

         // replace 4th occurance
         if ($counter++ == 4) {
              return "<img>";
         }

         return $m[0];

    }, $txt );
}

echo $txt;

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）$justit=ceil（$2/2）-1；来代替它的中间部分
<?php

$txt  = "Hello, Hello, how are you?
Hello, Hello, how are you?<br />
Hello,
Hello,<br />
How are you?
How are you today?
I am fine; I am great
I am fine;<br />
I am just great
I am fine; I am great
I'm very well today!<br />
Great!
Hello, Hello, how are you?<br />
Hello, Hello, how are you?
Hello, Hello, How are you?<br />
How are you today?";

$occurrences = substr_count($txt, '<br />');
if( 1 === $occurrences ) {
    $txt = str_replace('<br />', "<img>", $txt);
} else {
    $counter = 1;
    $txt = preg_replace_callback("/<br \/>/", function ($m) use (&$counter) {

         // replace 4th occurance
         if ($counter++ == 4) {
              return "<img>";
         }

         return $m[0];

    }, $txt );
}

echo $txt;